Car a is traveling at 40 mi/h when it enters a 30 mi/h speed zone. the driver of car a decelerates at a rate of 16 ft/s2 until reaching a speed of 30 mi/h, which she then maintains. when car b, which was initially 60 ft behind car a and traveling at a constant speed of 45 mi/h, enters the speed zone, its driver decelerates at a rate of 20 ft/s2 until reaching a speed of 28 mi/h. knowing that the driver of car b maintains a speed of 28 mi/h, determine (a) the closest that car b comes to car a, (b) the time at which car a is 70 ft in front of car b.